The Forever War

In the presence of limited good, and of corruptible man, what is our responsibility? Is it to use present evil on behalf of present good and thereby to ensure the continuation of evil? Or is it to deny present gain in an effort to destroy evil itself? 

The above questions are the underlying theme of The Lord Of The Rings (and has been happily appropriated from here), and are as true today as they were back then.
The more things change...